REVIVE THE CHEAP LED GARDEN LIGHT

After I helped Daniel, a brother at church, to revive his garden light.  He said I should share this in my blog. This is my way of reviving any garden LED light from "dim some" to "full brightness". Disclaimer: Your mileage may vary!

I am writing this blog with the STAR format.

Situation: The garden light set that I installed last year no longer working properly. My wife insisted that I fix it one week before the big family gathering.

Task: Make the garden light works - cheap!

Action:

- Took the light fixture apart to investigate the circuitry

- Determined that the solar cell and rechargeable battery are cheap components

- Replaced the rechargeable battery with regular alkaline AA battery.

Result: The light fixture was working as designed with full brightness - better than the 1^st day came out from the box. It was ON at sunset and OFF at sunrise for about three months. Happy wife! Happy life!

Deep Dive

Being an electronics engineer, I don’t want to buy another set of lights. I wanted to find the solution of the problem.

The LED garden light has the following components. They are

·         LED

·         Ni-Cad rechargeable battery

·         Solar Cell

·         Light sensor – photo cell

·         Electronic circuitry concealed in a Printed Circuit Board

Below is the block diagram of the solar cell powered garden light fixture

Circuit analysis:

·         The solar cell generates power to charge the rechargeable battery during day time when there is ambient light. The solar cell does not need to have direct sun light to work.

·         The photo cell determines when to turn ON and OFF the garden light (LED)

I have two observations:

1.       The solar cell does not generate enough “juice” to fully or partially charge the battery.

2.       The inexpensive rechargeable battery does not hold the charge for sustaining operation.

Replace the inexpensive battery with a decent battery would not fix the problem because the cheap solar cell is the problem.

My solution: 

Replace the rechargeable battery with a regular alkaline AA is a solution to the problem temporary. The cheap components of the not-so-long-lasting garden light is the problem. Without diving into how much electrical energy the solar cell can generate with normal ambient light, replacing the Ni-Cad with alkaline battery works for probably three months – try it!

Photo Gallery:

Top of most LED garden light

Remove the lens to find the battery compartment 

Remove the cover of the battery compartment

Replace the original NiCad battery with a regular alkaline battery

You are done - reassemble the garden light fixture. 

More pictures for the curious minded. 

Print Circuit Board (PCB) of most garden light with IC

Electronic of anther brand of garden light (courtesy of Daniel)

The original picture was dark - this one has three beautiful garden lights (courtesy of Daniel)